The present invention relates to a seal apparatus of a gear pump which is favorably used as, for example, a hydraulic source of a brake system for vehicle.
Japanese Utility Model Application Publication No. H03(1991)-123993 discloses a previously-proposed gear pump. The gear pump in this technique includes a drive shaft, a driven shaft, a pair of side plates and a seal member in a housing. Because the seal member is an elastic body, a backup ring having a higher hardness than the seal member is provided on a low-pressure side of the side plate (on an inner circumferential side of the side plate). Thereby, it is suppressed that the seal member is excessively deformed. The seal member and the backup ring are held to be sandwiched between the side plate and an inner surface of the housing.